There has heretofore been proposed a plastic bag including panel portions, side gusset portions and a bottom gusset portion, as disclosed in Japanese Patent Publication No. 3,655,627. Each of the panel portions has opposite side edges along which the side gusset portions extend. Each of the panel portions further has opposite end edges along one of which the bottom gusset portion extends. Each of the side gusset portions has opposite end portions at one of which an auxiliary gusset portion is formed. The bottom gusset portion is combined with the auxiliary gusset portion. The plastic bag can therefore be enlarged by the side gusset portions to obtain an increased capacity. A flat bottom surface can be formed by the bottom gusset portion to make the plastic bag stand stably. The plastic bag is called a rectangular bottom bag.
In addition to the side gusset portions and the bottom gusset portion, the plastic bag may further include an additional bottom gusset portion, as disclosed in Japanese Patent Publication No. 4,108,846. The bottom gusset portion extends along one of the end edges of panel portion while the additional bottom gusset portion extends along the other end edge. In addition to the auxiliary gusset portion formed at one of the end portions of side gusset portion, an auxiliary gusset portion is formed at the other end portion. The additional bottom gusset portion is combined with the auxiliary gusset portion. In this case, the plastic bag can be shaped into a rectangular parallelepiped to have an appearance of box when being filled with content. A flat top surface is formed by the bottom gusset portion while a flat bottom surface is formed by the additional bottom gusset portion. The plastic bag is therefore high in efficiency of being filled. The plastic bags can be pilled up conveniently.
The plastic bag of each of the publications is therefore expected to be used widely in the future. In this connection, it is desired to make the plastic bag have an added value. In particular, it is desired to make the plastic bag include an opening in position for discharge of content.
It is therefore an object of the invention to provide a new and improved apparatus for successively making plastic bags each of which is called a rectangular bottom bag.
Another object is to make the plastic bag include an opening in position.